1. Field of the Invention
This invention relates to a rotary blood pump having a housing, a stator and a rotor wherein the rotor is rotatably connected to the stator. More particularly, this invention concerns a rotary pump having a rotor rotatably connected to the stator and which incorporates a semiconductor-based electronic component to draw heat created by the frictional contact between the rotor and the stator away from the rotor thus, preventing coagulation and destruction of blood flowing through the rotary pump.
2. Description of the Related Art
One type of conventional axial flow rotary pump 10, shown in FIG. 1, comprises a pump housing 12 which defines a blood flow path 14 and which houses a rotor 16 and stator members 18. The rotor 16 is substantially cylindrical with a tail 20 and a nose 22 and has impeller blades 24 extending from the rotor 16. A contact-type bearing 25 is positioned at the nose 22 and another contact-type bearing 27 is positioned at the tail 20. Contact-type bearings may be (a) roller-type, (b) journal-type, or (c) pivot-type. The journal-type comprises bearings implementing a hydrodynamic film, typically annular for radial loads, or disk-like for thrust loads. This type of bearing is illustrated in U.S. Pat. No. 4,994,078 issued to Jarvik and U.S. Pat. No. 5,275,580 issued to Yamazaki et al. The pivot-type comprises bearings using either point contact (like jewel bearings used in clock mechanisms) or a ball-and-cup connection. This type of bearing is illustrated in U.S. Pat. No. 5,588,812 issued to Taylor et al., U.S. Pat. No. 5,527,159 issued to Bozeman Jr., et al. and U.S. Pat. No. 5,575,630 issued to Nakazawa et al. For the purposes of this discussion, a pivot-type ball-and-cup bearing will be assumed, although any of the aforementioned contact-type bearings are applicable.
The stator member 18 located at the inlet 30 has stator inlet blades 32 and a cup 34 which engages the ball 26 of the rotor 16. The other stator member 18 located at the outlet 36 includes outlet stator blades 38 and a cup 40 which engages the ball 28 of the rotor 16. A lubricant (either manufacturing fluid, purge fluid, or some constitutive component of blood) fills the gaps created between the ball and cup members 26, 28, 40 and 34. In operation, electrical power is supplied to the motor stator 42 through cable 44 and the motor stator 42 along with the motor rotor 46 imparts rotational movement to the rotor 16 such that blood is pumped through the blood flow path 14 by the motion of the rotor blades 24.
The disadvantage of this type of pump is that the mechanical frictional contact and/or viscous dissipation between the contact-type bearing members creates heat at the bearing interface which may result in coagulation and destruction of blood flowing through the housing blood flow path. Furthermore, the coagulated blood can accumulate in the bearing gap causing seizure.
Nowhere in the cited related art is there disclosed or suggested a rotary pump having a rotor which is rotatably connected to a stator and which provides for the dissipation of heat created from this frictional contact thus, minimizing thermally induced destruction and coagulation of blood. Therefore, there is a definite need for a rotary blood pump which incorporates a semiconductor-based electronic component that dissipates heat created by the frictional contact between the stator and the rotor thus, minimizing damage to the blood flowing through the pump.